title: The (R)-enantiomer of CE3F4 is a preferential inhibitor of human exchange protein directly activated by cyclic AMP isoform 1 (Epac1).
abstract: Isoform 1 and isoform 2 of exchange protein directly activated by cAMP (Epac1 and Epac2) contribute to cAMP signaling in numerous cellular processes. Their guanine-nucleotide exchange factor (GEF) activity toward the small GTP-binding protein Rap1 is stimulated by the agonist cAMP. CE3F4, a tetrahydroquinoline analog, prevents Epac1 activation in vitro and in living cultured cells by inhibiting the GEF activity of Epac1. However, the activity of the (R)- and (S)-enantiomers of CE3F4, as well as the ability of CE3F4 and its analogs to inhibit Epac2 GEF activity, have not yet been investigated. In this study, we report that (R)-CE3F4 is a more potent cAMP antagonist than racemic CE3F4 and (S)-CE3F4, inhibiting the GEF activity of Epac1 with 10-times more efficiency than (S)-CE3F4. Epac2, in contrast to Epac1, is activated more efficiently by cAMP than by 8-(4-chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (007), an Epac-selective cAMP analog. (R)-CE3F4 displays Epac isoform preference, with 10-fold selectivity for Epac1 over Epac2. Deletion of the N-terminal cyclic nucleotide-binding domain of Epac2 does not affect the characteristics of activation of Epac2 by cAMP and by 007, nor its inhibition by CE3F4. Finally, the evaluation of a series of CE3F4 structural analogs as GEF inhibitors allowed identifying structural features that are important for high Epac1 inhibitory activity of CE3F4. We conclude that the (R)-enantiomer of CE3F4 is a preferential inhibitor of Epac1 with high potency in the low micromolar range, and we suggest that this compound may be a useful pharmacological tool for investigating the functional role of Epac1 in cAMP signaling.
authors.affiliation: Univ Paris-Sud, CIBLOT-IFR 141, Faculté de Pharmacie, 92296 Châtenay-Malabry Cedex, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Courilleau
authors.forename: Pascal
authors.initials: P
authors.lastname: Bouyssou
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Fischmeister
authors.forename: Frank
authors.initials: F
authors.lastname: Lezoualc'h
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Blondeau
mesh_terms: D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors*; D006801:Humans; D007536:Isomerism; D020033:Protein Isoforms / Q000037:antagonists & inhibitors; D011804:Quinolines / Q000494:pharmacology*
chemical_list: C588037:6-fluoro-5,7-dibromo-2-methyl-1-formyl-1,2,3,4-tetrahydroquinoline; D020662:Guanine Nucleotide Exchange Factors; D020033:Protein Isoforms; D011804:Quinolines; C116122:RAPGEF3 protein, human
keywords: 007; 6-Fluoro-5,7-dibromo-2-methyl-1-formyl-1,2,3,4-tetrahydroquinoline; 8-(4-chloro-phenylthio)-2′-O-methyl-cAMP; CE3F4; CNB; DEP; Disheveled/Egl-10/Pleckstrin; Drug enantiomers; Epac; Epac inhibitor; GEF; PKA; Rap1 GEF; Tetrahydroquinoline analogs; cAMP signaling; cyclic nucleotide binding; exchange protein directly activated by cyclic AMP; guanine-nucleotide exchange factor; protein kinase A